San Gabriel Valley · LA County
ADU permits in San Dimas
Zip codes:91773
San Dimas is an independent city of about 34,000 people in the eastern San Gabriel Valley (SGV), at the base of the San Gabriel Mountains foothills. It runs its own building and planning departments. The city is anchored by Frank G. Bonelli Regional Park (a 1,975-acre LA County park with Puddingstone Reservoir) and by the Raging Waters water park.
Independent city — not LADBS
San Dimas runs its own building department. Permits go through San Dimas Community Development Department ↗, not the Los Angeles Department of Building and Safety (LADBS). Our address checker pulls real zoning + overlay data for any Los Angeles County address. The San Dimas ordinance breakdown below covers the city-specific permit path.
San Dimas by the numbers
Rounded figures from the 2020 US Census, LA County Assessor parcel data, and the city's own published reports. Estimates only — your specific lot can vary widely.
Population
34,000
2020 Census
Single-family homes
~10,800
LA County Assessor
Median lot size
8,000 sqft
Approximate
Median home value
$0.9M
Zillow / Redfin
What makes San Dimas different
San Dimas's ADU ordinance is in San Dimas Municipal Code Title 18. The city aligns with the California state baseline plus Hillside Standards. Plan check is typically 60 days. The city retains a Western-history theme reflected in downtown architecture and the annual Western Days festival.
San Dimas ADU ordinance — the rules that apply
Last verified: 2026-05-12
The current ADU rules in San Dimas, sourced from the city's published ordinance and verified against CA Government Code §65852.2 (which preempts local rules stricter than state baselines). When you see "state default," that means the city can't reduce below this number under state law.
| Max detached ADU size | 1,200 sqft (state default) |
| Max ADU height | 16 ft / 18 ft with second-story setbacks |
| Setbacks | 4 ft side / 4 ft rear (state minimum) |
| Hillside Standards | Apply on slopes over 10% |
| Western architectural theme | Suggested for parcels in or adjacent to downtown |
| Local processing time | 60 days for standard ADUs |
| Pre-approved standard plans | None city-specific |
Active overlays + extra rules in San Dimas
City overlays + state-level designations that hit a meaningful share of San Dimas parcels. Each affects what you can build, how long it takes, or how much it costs.
Hillside Standards
~25% of parcelsSlopes over 10% trigger geotech + grading limits.
Watch-outs specific to San Dimas
Patterns we see across San DimasADU permits. None are dealbreakers — they're just the things people get wrong most often.
- 01
Bonita Unified school fees apply
Bonita Unified School District (BUSD) — shared with La Verne — charges school facility fees on ADUs over 500 sqft.
Need a person, not a wizard?
Routes that fit San Dimas
Based on what we know about San Dimas, these are the lead types that usually make sense here. Pick whichever fits your situation. All free, no obligation.
Complex permit context
Request a San Dimas permit referral
Coastal, hillside, historic, fire-zone, or multi-overlay parcels in San Dimas usually mean a permit expediter pays for itself in saved months. We work with vetted Los Angeles permit expediters and expeditors (both spellings) who've handled San Dimas projects.
Complex permit context
Request a San Dimas permit referral
Coastal, hillside, historic, fire-zone, or multi-overlay parcels in San Dimas usually mean a permit expediter pays for itself in saved months. We work with vetted Los Angeles permit expediters and expeditors (both spellings) who've handled San Dimas projects.
Plans that fit San Dimas lots
San Dimasdoesn't maintain a city-specific pre-approved plan library the way the Los Angeles Department of Building and Safety (LADBS) does. California Department of Housing and Community Development (HCD)-approved prefab (which bypasses local plan check) and custom designer plans are the main paths:
Amenities + civic services in San Dimas
Parks, libraries, and the school district that serve the area. Context that matters for renter appeal, family relocation, and long-term resale.
Parks + sports
Frank G. Bonelli Regional Park
Puddingstone Reservoir, central San Dimas
1,975-acre LA County regional park with the 250-acre Puddingstone Reservoir. Hiking, fishing, biking, the Raging Waters water park.
1,975-acre LA County regional park
- Fishing
- Trails
- Playground
- Picnic
San Dimas Canyon Park
San Dimas Canyon Road, north San Dimas
Foothill park with hiking trails into the Angeles National Forest.
- Trails
- Picnic
Libraries
San Dimas Library
LA County Library
Walnut Avenue, central San Dimas
Public schools
School assignments vary by exact address. The district + notable schools below cover most of the area.
District
Bonita Unified School District (BUSD)
Notable schools in the area
- San Dimas High School
- Lone Hill Middle
Getting around San Dimas
Car-dependent. Foothill Transit serves major corridors.
Transit + walkability
Bus lines
- Foothill Transit Routes 480 + 690
Nearest rail
Metro A Line — Future San Dimas station (planned, under construction)
Walkability
Downtown San Dimas + Bonita Avenue corridor are walkable. Foothill is car-dependent.
Nearby airports
Distance + type for each major Los Angeles-area airport reachable from San Dimas. Useful for travel, commute, and any flight-path noise concerns on specific parcels.
Brackett Field (POC)
~4 miGeneral aviation
Ontario International (ONT)
~12 miInternational
Community + landmarks in San Dimas
Annual events, landmarks, and the places that anchor the area's identity. Context for renter appeal and long-term resale.
Annual events
San Dimas Western Days
Spring (one weekend)
Annual Western-history themed community festival in downtown San Dimas.
Source ↗
What makes San Dimas San Dimas
Water park
Raging Waters
Major regional water park inside Frank G. Bonelli Regional Park. Largest water park in California.
Regional park
Frank G. Bonelli Regional Park + Puddingstone Reservoir
1,975-acre LA County park with a 250-acre reservoir. Major regional destination.
Nearby areas to San Dimas
Other Los Angeles-area pages worth a look. Each one runs different Accessory Dwelling Unit (ADU) rules depending on jurisdiction — we show you what changes when you cross a city or county line.
Independent city
La Verne →
Mid-tier home values, University of La Verne employment base, and an upcoming Metro A Line (Gold Line) extension station make La Verne a solid Accessory Dwelling Unit (ADU) market at a more accessible price point than the western SGV.
Independent city
Glendora →
Foothill lots, top-rated Glendora Unified School District (GUSD), and the walkable Glendora Village give Glendora steady Accessory Dwelling Unit (ADU) demand. Northern foothill parcels qualify for premium home-value pockets driving financing-broker interest.
Frequently asked questions about San Dimas ADUs
›Can I build an ADU in San Dimas?
Yes. San Dimas allows ADUs under its local ordinance, aligned with California Government Code §65852.2 (the state baseline that preempts overly-strict local rules). Most single-family lots can host one ADU plus one JADU. Permits go through San Dimas Community Development Department, not LADBS — see the ordinance table above for the specific rules.
›How does San Dimas differ from LA City for ADU permits?
Three main differences: the permit agency (San Dimas Community Development Department vs. LADBS), the local ordinance details (each city has some flexibility above the state baseline), and the timeline (some cities are faster, some slower than LA's 60-day plan check). See the ordinance breakdown above for the specifics on each.
›How much does it cost to build an ADU in San Dimas?
Median home value in San Dimas is around $0.9M, which usually means lot economics support a quality ADU build of $200K–$400K all-in. Hillside, coastal, or VHFHSZ lots add 7–25% on top. HCD-prefab units (Connect Homes, Cover, Plant Prefab) bypass local plan check entirely and typically run $190K–$350K turnkey.
›Does San Dimas have pre-approved standard plans like LA's YOU-ADU?
No. Unlike LADBS, San Dimas does not maintain a city-specific pre-approved plan library. The two faster paths are an HCD-approved prefab (factory-certified, skips local plan check) or a custom designer drawing for your lot. The slower path is a fully custom architect-led design.
›Will the PermitPathLA wizard work for my San Dimas address?
Yes. The wizard pulls real zoning, overlay, and parcel data for any Los Angeles County address, including San Dimas. What you'll see today: feasibility for your specific lot, the overlays that apply, and a routing summary pointing at San Dimas Community Development Department for the permit submittal. Deeper San Dimas-specific permit walkthroughs are next on the roadmap as we expand from LADBS into the independent-city ordinances.
Ready to see what your San Dimas lot can do?
Our free address checker pulls real zoning, overlay, and parcel data for any Los Angeles County address — including San Dimas. Start there and we'll surface what applies to your specific lot.
Check your address →Reviewed by Yair Harpaz, Founder, PermitPathLA. California DRE-licensed broker with 30+ years of Los Angeles real estate and mortgage industry experience.
San Dimas ordinance data last reviewed .
See an error or stale rule? corrections@permitpath.la
Primary sources: San Dimas planning · San Dimas Community Development Department permits